Rhododendron plant named &#39;WALSNOWRUF&#39;

ABSTRACT

A new and distinct variety of  Rhododendron  plant named ‘WALSNOWRUF’ which is characterized by compact mounding habit, glossy evergreen foliage, large double bright white flowers which are produced from early summer through early fall (July to September approximately), is disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. 119 of U.S. Provisional Application No. 61/956,954 filed on Jun. 20, 2013 entitled “Rhododendron Plant Named ‘WALAZ06’” and for which the inventor now wishes to file this application with the cultivar name or denomination ‘WALSNOWRUF’.

GENUS AND SPECIES

Rhododendron kaempferi hybrid

VARIETY DENOMINATION

‘WALSNOWRUF’

BACKGROUND OF THE NEW PLANT

The present invention relates to a new and distinct cultivar of Rhododendron, also commonly known as evergreen azalea, which is grown as an ornamental shrub for use in planted containers and in the garden and landscape. The new cultivar is known botanically as Rhododendron kaempferi hybrid, and will be referred to hereinafter by the cultivar name ‘WALSNOWRUF’.

‘WALSNOWRUF’ arose and was selected from a long term breeding program commenced by the inventor in 1993 or 1994. The aim of the breeding program was to develop one or more matched series of novel cultivars of hardy evergreen azaleas with showy flowers, large open-faced single flowers, and also heavily flowering double flower forms. Breeding commenced with Azalea ‘Elsie Lee’ as one of the initial parents. Azalea ‘Elsie Lee’ is a Shammarello hybrid, raised in Ohio in the 1960s and renowned for its relative hardiness among evergreen azaleas. Although several Shammarello hybrids were patented in the 1960s and 1970s, the inventor believes that Azalea ‘Elsie Lee’ was unpatented. ‘Elise Lee’ bears light mauve-blue semi-double flowers.

Commencing in 1993 or 1994, many generations of deliberate hybrids were raised, selecting promising parents from his collection of previous unnamed seedlings which had been raised during the breeding program. The inventor selected ‘WALSNOWRUF’ in 2003 or 2004. The parents of ‘WALSNOWRUF’ are unknown to the inventor and have not been retained. Thus, no parental comparison information is available.

Asexual propagation of ‘WALSNOWRUF’ was first accomplished by the inventor in 2003 or 2004 using semi-ripe shoot cuttings. Since that time, under careful observation, the distinguishing characteristics of ‘WALSNOWRUF’ have been determined stable and uniform, and to reproduce true to type in successive generations of asexual propagation via semi-ripe shoot cuttings.

SUMMARY OF THE NEW VARIETY

The distinguishing characteristics of ‘WALSNOWRUF’ are listed below. ‘WALSNOWRUF’ has not been tested under all possible conditions and phenotypic differences may be observed with variations in environmental, climatic, and cultural conditions.

-   -   1. Plants of ‘WALSNOWRUF’ exhibit a compact mounding growth         habit.     -   2. The foliage of ‘WALSNOWRUF’ is glossy evergreen in color.     -   3. ‘WALSNOWRUF’ bears large double flowers in a crisp white         color.     -   4. Plants of ‘WALSNOWRUF’ show good heat and humidity tolerance.     -   5. ‘WALSNOWRUF’ blooms from early summer through early Fall.         (July to September approximately)     -   6. After two years of growth, plants of ‘WALSNOWRUF’ are 25 cm         to 30 cm in height and 25 cm to 30 cm in width.     -   7. At maturity, 5 years, plants of ‘WALSNOWRUF’ are 30 cm to 40         cm in height and 30 cm to 40 cm in width.     -   8. ‘WALSNOWRUF’ prefers semi-shade in a moist, well drained,         slightly acidic growing media.     -   9. ‘WALSNOWRUF’ is suitable for use as a garden specimen,         landscape plants and as a container specimen.     -   10. ‘WALSNOWRUF’ is hardy to at least USDA Zone 7.

DESCRIPTION OF THE PHOTOGRAPHS

The accompanying color photographs illustrate the overall appearance of ‘WALSNOWRUF’ showing the colors of its foliage and flowers as true as it is reasonably possible to obtain in colored reproductions of this type. Both photographs were taken in May 2013 from one-year old plants which have been grown outdoors in 3-liter containers in the inventor's nursery in Arundel, West Sussex, United Kingdom.

FIG. 1 depicts a whole plant of ‘WALSNOWRUF’.

FIG. 2 depicts a close-up view of the flower of ‘WALSNOWRUF’.

BOTANICAL DESCRIPTION OF THE PLANT

The following is a detailed description of ‘WALSNOWRUF’. The observed plant was 2-years old and was growing out of doors in a 1-gallon container in Santa Barbara, Calif. where the botanical description was made in May 2014. The color determinations are in accordance with the 2007 edition of the Colour Chart of The Royal Horticultural Society, London, England, except where general color terms of ordinary dictionary significance are used. Growing conditions are similar to those of other Rhododendron.

-   Botanical classification:     -   -   Family.—Ericaceae.         -   Genus.—Rhododendron.         -   Species.—kaempferi hybrid.         -   Cultivar.—‘WALSNOWRUF’. -   Parentage: Un-named seedlings raised during the breeding program;     parents not retained or described -   Plant:     -   -   Commercial classification.—Perennial.         -   Common name.—Evergreen azalea.         -   Use.—Ornamental for container or landscape.         -   Cultural requirements.—Plant in partial shade and any             free-draining slightly acidic soil.         -   Particular pest resistance or susceptibility.—None observed.         -   Propagation method.—Semi-ripe cuttings without use of             rooting hormone.         -   Rooting system.—Fine and fibrous.         -   Vigor.—Moderately vigorous; lateral branching is encouraged             by pinching.         -   Habit.—Low mound.         -   Dimensions after two years.—25 cm to 30 cm in height and 25             cm to 30 cm in width.         -   Dimensions after five years.—30 cm to 40 cm in height and 30             cm to 40 cm in width.         -   Hardiness.—USDA Zone 7. -   Stem:     -   -   Dimensions.—Length 1.5 cm (height of manual pinch); diameter             at base: 1 cm.         -   Shape.—Cylindrical.         -   Bark.—Rough, color 177A.         -   Number of branches.—12. -   Branches (current season extension growth):     -   -   Shape.—Cylindrical.         -   Surface.—Sparsely pubescent.         -   Dimensions.—Length: 18 cm to 20 cm, diameter 3 mm.         -   Color.—144B.         -   Internode length (range).—1.0 cm to 1.5 cm. -   Branches (previous year's growth):     -   -   Shape.—Cylindrical.         -   Dimensions.—Length: 15 cm to 20 cm, diameter 3 mm.         -   Color.—172A.         -   Bark surface.—Rough.         -   Internode length (range).—1.0 cm to 2.0 cm. -   Foliage:     -   -   Type.—Evergreen.         -   Leaf arrangement.—Alternate.         -   Leaf division.—Simple.         -   Leaf dimensions (average, fully developed).—6 cm in length             and 3 cm in width.         -   Leaf color (current season new growth, adaxial             surface).—141B.         -   Leaf color (current season new growth, abaxial             surface).—143C.         -   Leaf color (mature, previous year's growth, adaxial             surface).—136A.         -   Leaf color (mature, previous year's growth, abaxial             surface).—138A.         -   Leaf shape.—Elliptic, base cuneate, apex obtuse.         -   Leaf margin.—Ciliate, hairs fine, 1 mm, silver-gray 156D.         -   Leaf surface (both surfaces).—Smooth, glossy, sparsely             pubescent, hairs fine, 1 mm, silver-gray 156D.         -   Venation.—Pinnate, color 141B.         -   Petioles.—Dimensions: 5 mm in length, 1.5 mm to 2.0 mm in             width Color: 144A. -   Inflorescence:     -   -   Inflorescence type.—Terminal.         -   Flower arrangement.—Flowers in groups of 8 to 12.         -   Flower aspect.—Upward or outward.         -   Form.—Rotate.         -   Inflorescence quantity.—Ranges between 3 and 5 per branch             and between 30 and 50 at peak of flowering.         -   Dimensions of inflorescence (average).—10 cm in diameter, 8             cm in depth.         -   Blooming season.—Early summer through early fall (July to             September approximately).         -   Lastingness of flowers (on the plant).—7 to 10 days. -   Bud:     -   -   Arrangement.—Borne in clusters of 8 to 12 buds; initially,             each bud is sheathed by a pair of modified leaf bracts which             fall away as the bud swells.         -   Bud shape.—Ovoid.         -   Dimensions (immediately prior to opening).—12 mm in length             and 10 mm in diameter.         -   Bracts (bud sheath).—Pair, each 18 mm in length, 15 mm in             width.         -   Bracts (bud sheath).—Shape cupped, texture paper-like, base             truncate, apex acute.         -   Bract color (adaxial surface).—Base 155C, becoming 142C and             142B at apex; in addition, dorsal (convex) surface 163A.         -   Bract color (abaxial surface.—Base 155C, becoming 142C and             142B at apex.         -   Bud color (as bracts fall away, as bud opens).—149D.         -   Sepals.—5 in number, fused at base.         -   Sepal color (both surfaces).—144A, surface pubescent, hairs             fine, 1 to 2 mm, silver-gray 156D.         -   Sepal dimensions.—Length: 7 mm; width: 5 mm.         -   Sepal shape.—Ovate, base rounded, apex cuspidate.         -   Sepal surface.—Pubescent, many fine hairs 1 mm to 2 mm,             silver-gray 156D.         -   Pedicel.—Length 14 mm, width 2 mm.         -   Pedicel surface.—Pubescent, many fine hairs 1 mm to 2 mm,             color 144A. -   Flowers:     -   -   Form.—Semi-double, initially cylindrical, becoming globose.         -   Flower dimensions.—5.5 cm to 6.0 cm in diameter, 3.0 cm in             depth.         -   Petal arrangement.—Three whorls, each whorl consisting of 5             petals fused at base; inner whorl occasionally modified to             anther-bearing petaloid stamens.         -   Petal shape.—Widely ovate, base truncate, apex rounded.         -   Petal dimensions.—Outer whorl: 35 mm in length, 25 mm in             width Second whorl: 28 mm in length, 22 mm in width Inner             whorl: 25 mm in length, 20 mm in width.         -   Petal margin.—Smooth, gently ruffled.         -   Petals.—Color (both surfaces): White (whiter than NN155D),             base 150C Spots: Occasionally present on adaxial surface as             short dashes towards petal base, length 1 mm to 2 mm, width             0.5 mm to 1.0 mm, color 150C Surface: Smooth, glossy.         -   Venation.—Parallel, color 136A.         -   Peduncle.—Dimensions: 5 mm in length, 2 mm in width, ribbed             Surface: Smooth Color: N144D. -   Reproductive organs:     -   -   Petaloid stamens (when so modified).—1 to 9 in number,             length: 25 mm, width 20 mm, color white, (whiter than             NN155D).         -   Anthers.—Shape is oblong, bifid, length 3 mm, width 1.0 mm             to 1.5 mm, color 167D.         -   Pollen.—Absent.         -   Pistil.—Length 5 mm, diameter 0.5 mm, color 138C.         -   Stigma.—Color 137B.         -   Ovary.—Ovate, 4 mm in length, 3 mm in diameter; surrounded             by dense very fine silver-gray hairs, length 5 mm, color             nearest 156D. -   Seed set: None observed.

Comparison with Commerical Variety

‘WALSNOWRUF’ may be compared with Azalea ‘Honesty’ (U.S. Plant Pat. No. 12,054) which also bears double pure white flowers. ‘Honesty’ is a florist or greenhouse azalea and is not hardy, whereas ‘WALSNOWRUF’ has been observed to tolerate temperatures as low as −15° C. (USDA Hardiness Zone 7). In addition, the flowers of ‘Honesty’ are very large, up to 9 cm in diameter, whereas the flowers of ‘WALSNOWRUF’ are typically 5.5 cm to 6.0 cm in diameter.

In addition, ‘WALSNOWRUF’ may be compared with Azalea ‘April Gem’ (unpatented) which is a white double-flowered Mehlquist hardy hybrid. The flowers of ‘April Gem’ are borne singly or in clusters of 2 to 4 flowers whereas the flowers of ‘WALSNOWRUF’ are arranged in large clusters, typically between 8 and 12 flowers per inflorescence. Finally, the flowers of ‘April Gem’ are smaller (diameter 4 cm to 5 cm) than the flowers of ‘WALSNOWRUF’, and are generally described as slightly fragrant whereas no fragrance has been observed in WALSNOWRUF’. 

I claim:
 1. A new and distinct variety of Rhododendron plant named ‘WALSNOWRUF’ as described and illustrated herein. 